1. Field of the Invention
This invention relates to a recording method for recording data on an optical disc and a recording and/or reproducing apparatus for recording and/or reproducing data on or from an optical disc.
2. Description of Related Art
Heretofore, an optical disc called a DVD (digital versatile disc) is furnished as an optical disc convenient for multi-media usage. In this optical disc, the recording capacity is appreciably increased due to the small pitch of the recording track or the data compression technique.
This optical disc copes with a wide field of application encompassing video data, audio data or computer data. This optical disc is used as a replay-only data recording medium in which data is formed as pits. This optical disc is called a DVD-ROM.
There has also been furnished an interchangeable recordable optical disc which can be reproduced on a reproducing apparatus adapted to cope with this optical disc. Specifically, the formats for a DVD+RW (DVD+Rewritable), DVDxe2x88x92RW (DVD-Rewritable) and DVD-R (DVD-Recordable) on which data can be recorded only once.
In recording and/or reproducing these optical discs, tracking error signals indicating the deviation from the recording track of a converging point of the laser light are generated to follow the recording tracks or row of pits carrying the recorded data.
The tracking error signals are generated in accordance with the three spot system, differential push-pull PPP system or the differential phase detection DPD system. Specifically, the tracking error signals are generated based on detection signals obtained by a light receiving section 101 shown in FIG. 1.
The light receiving section 101 is made up of four split areas SA, SB, SC and SD and two areas each split into two, namely areas SE, SF, SG and SH.
The light receiving section 101 is provided on an optical pickup facing the signal recording surface of the optical disc, and is fed with the reflected laser light from the optical disc. From the respective areas SA, SB, SC, SD, SE, SF, SG and SH of the light receiving section 101 are output RF signals A, B, C, D, E, F, G and H associated with the received light quantities.
In the three-spot system, the laser light is split using a diffraction grating to generate three spots along a recording track formed on a signal recording surface of the optical disc. The tracking error signals TE3SP of the three spot system are generated by operational processing of
TE3SP=(E+F)xe2x88x92(G+H). 
In the DPP system, the laser light illuminated on an optical disc is split using a diffraction grating to generate three spots along the recording track formed on the signal recording surface of the optical disc. In the DPP system, tracking error signals TEDPP are generated by a circuit shown in FIG. 2. In this circuit, the tracking error signals TEDPP are generated by operational processing:
TEDPP={(A+D)xe2x88x92(B+C)}xe2x88x92{(F+H)xe2x88x92(E+G)}. 
That is, the result of an operation (F+H)xe2x88x92(E+G) is calculated from the signals E, F, G and H in a first difference taking unit 102, whilst the result of an operation (A+D)xe2x88x92(B+C) is calculated from the signals A, B, C and D in a second difference taking unit 104. The aforementioned tracking error signals TEDPP is calculated from the results of the above operational processing.
In the DPD system, the tracking error signals are generated on reception of the laser light radiated towards and reflected back from the pits on the optical disc.
In the DPD system, the tracking error signals TEDPD are generated by a circuit shown in FIG. 3. In this circuit, the signals A, B, C and D from the light receiving section 101 are filtered by filters 105a, 105b, 105c and 105d and made into a bi-level signal on level comparison to a reference potential VC in comparators 106a, 106b, 106c and 106d. 
The results of comparison in the level comparators 106a, 106b are phase-compared in a phase comparator 107a, whilst the results of comparison in the level comparators 106c, 106d are phase-compared in a phase comparator 107b. The results of comparison in these phase comparators 107a, 107b are integrated by an integrating circuit 108 to give the tracking error signals TEDPD.
The filters 105a, 105b. 105c and 105d are made up of a high-pass filter HP109 for cutting off dc components and two band-pass filters 110, 111 for amplifying EFM signal components.
The outputs of the band-pass filters 110, 111 are of different frequency response, as shown in FIG. 5. An output selection switch SWDPD switches between these outputs.
In capturing data from the optical disc, tracking error signals by the DPD system are used. The DPD system has been selected as giving the best signal in consideration of the offset or tilt of the optical disc and the lens movement.
Meanwhile, a recording apparatus adapted for coping with a recordable optical disc, such as DVD+RW, DVDxe2x88x92RW or DVD-R, data are recorded so that the data will be reproduced by a reproducing apparatus adapted for coping with a replay-only optical disc, such as DVD-ROM.
This recording apparatus applies the servo, such as tracking servo or focussing servo to the recordable optical disc, in its non-recorded state, to generate the timing for recording. Since no pits are formed in an optical disc in which no data has been recorded, the aforementioned recording apparatus controls the servo in a manner different from the aforementioned reproducing apparatus, that is with the use of a method for generating tracking error signals using a recording track. Moreover, the recording apparatus generates the timing for recording the data using signals not detectable by the aforementioned reproducing apparatus, such as wobbling of the grooves formed as recording tracks.
The aforementioned reproducing apparatus generates tracking error signals in accordance with the DPD system of detecting the reflected light from the pits recorded on the replay-only optical disc. From the reproduced data, synchronization signals are detected by the PLL (phase-locked loop) to generate the timing signals pertinent to reproduction.
On the other hand, the recording apparatus generates tracking error signals from the recording track in accordance with the DPP system. The data write timing is acquired using an ADIP (address in pre-groove) signal, recorded by modulating the groove of the recording track at a low speed, followed by wobbling, and also using fine clock marks, obtained on high-speed modulation. Meanwhile, this timing can be used not only during recording but also during reproduction.
In light of the above, it may be an occurrence that a recordable optical disc, on which data has been recorded by the above-described recording apparatus, cannot be reproduced by the above-mentioned reproducing apparatus adapted for coping with the replay-only optical disc. For example, assume that there is portion of the recordable optical disc, if small, in which pits have not been recorded appropriately. With the aforementioned recording apparatus, there is raised no particular problem if the unreadable portion is in a range of possible error correction, even though the portion cannot be read correctly. However, there may be an occasion where tracking error signals are generated by the DPP method by the presence of the groove, but the generation of the tracking error signals by the DPD method becomes difficult to disable the servo control and the readout of such portion.
The same applies for the timing. That is, in the aforementioned recording apparatus, timing compensation becomes possible by the timing generated by ADIP or ATIP even though timing generation cannot be made by the signal from the pits recorded and/or reproduced, whereas, in the aforementioned reproducing apparatus, such compensation is not possible, thus again disabling the readout.
In particular, in a format of a recordable optical disc, or a so-called DVDxe2x88x92RW format, there are link portions where pits are not necessarily formed satisfactorily due to material flow or laser power adjustment. The possibility of occurrence of such a phenomenon that the timing is not generated satisfactorily in this portion with the signals from the pits is not that low.
Stated differently, it is possible with the aforementioned recording apparatus to adjust the data extraction timing by taking advantage of the groove wobbling information. However, the reproducing apparatus is able to reproduce only the timing information derived from the recorded data.
In the so-called DVD-R or DVDxe2x88x92RW, there in no link portion, however, the above-mentioned phenomenon is still liable to occur from time to time.
Of course, data is recorded on the recordable optical disc under a pre-set condition which is determined to present no problem on reproduction by the aforementioned reproducing apparatus. Nevertheless, there is still a possibility that the above-described phenomenon occurs due to a variety of recording conditions and operational disturbances.
That is, there is a risk that an optical disc, on which recording has been made by the aforementioned recording apparatus adapted for coping with the recordable optical disc, cannot be reproduced correctly by the aforementioned respective apparatus adapted for coping with the replay-only optical disc.
It is therefore an object of the present invention to provide a recording method and apparatus for recording data on a recordable optical disc so that the data will be reproduced reliably by a reproducing apparatus adapted for coping with the replay-only optical disc.
In one aspect, the present invention provides a recording method in which a data readout system for a recordable optical disc differs from a data readout system for a replay-only optical disc, in which the method includes a recording step for recording data on the recordable optical disc and a verifying step of reading out the recordable optical disc having data recorded thereon in the recording step by a data readout system conforming to the standard for the replay-only optical disc for verification.
In another aspect, the present invention provides a recording and/or reproducing apparatus in which a data readout system for a recordable optical disc differs from a data readout system for a replay-only optical disc, in which the apparatus includes recording means for recording data on the recordable optical disc and readout means for reading out the recordable optical disc having data recorded thereon by the recording means by a data readout system conforming to the standard for the replay-only optical disc.
According to the present invention, in recording by a recording apparatus adapted for coping with a recordable optical disc, such as DVD+RW or DVD-R, the reproducing system in verifying pits of recorded data is adapted to the reproducing system adapted to cope with the replay-only optical disc, such as the DVD-ROM.
According to the present invention, the optical disc on which data has been recorded by a recording apparatus adapted to cope with a recordable disc, such as DVD+RW, can be reliably reproduced by a reproducing apparatus adapted to cope with the replay-only optical disc, such as DVD-ROM. Moreover, according to the present invention, since it is unnecessary to add a new circuit to the recording apparatus adapted to cope with the replay-only optical disc, such as DVD-ROM, there is no risk of raising the cost.